1. Field of the Invention
The present invention relates to a deck cross-member for use in, for example, automobiles. The invention relates also to a method of manufacturing a deck cross-member for use in, for example, automobiles.
2. Description of the Related Art
In any automobile, a deck cross-member stretches between the front pillars that are arranged on both sides, spaced apart in the widthwise direction of the automobile. The deck cross-member supports the shaft part of the steering unit. In view of this, rigidity of the deck cross-member may be enhanced in order to support the shaft part more rigidly.
In order to enhance the rigidity of the deck cross-member, the cross section of the deck cross-member may be increased.
Most deck cross-members are constituted by a pipe, however. The pipe has been produced by extrusion molding. A pipe made by extrusion molding usually has a section that is uniform in the axial direction, in a plane view perpendicular to the axis.
Therefore, there is the tendency that a deck cross-member constituted by a pipe has a cross section that is large enough to support of the shaft a steering unit rigidly and reliably.
The deck cross-member thus made can indeed support the steering unit more rigidly. However, its weight increases. As its weight increases, its manufacturing cost rises. Hence, the increase in the weight of the deck cross-member is not desirable.
In view of this, there has been proposed a deck cross-member that can more rigidly support the shaft part of a steering unit, without increasing its weight so much.
More specifically, this deck cross-member comprises a pipe having a large cross section and a pipe having a small cross section. The pipe having the large cross section is arranged at the side closer to the driver's seat. The pipe having the small cross section is arranged at the side closer to the passenger's seat. Some deck cross-members of this type have been proposed.
A deck cross-member of this type comprises a pipe that has a large cross section, because it is to be arranged at the side closer to the driver's seat and needs to support the steering unit rigidly. The pipe therefore improves the rigid supporting of the steering unit. The deck cross-member has a pipe that has a small cross section, because it is to be arranged at the side closer to the passenger's seat and does no serve so much to support the steering unit rigidly. This pipe therefore helps to reduce the weight of the deck cross-member. Such a deck cross-member is disclosed in Japanese Patent KOKAI Publication No. 9-277961.
One of the pipes constituting a deck cross-member of this type is expanded or contracted in terms of diameter, and the pipes are fitted one into the other. The two pipes are thereby coupled with each other.